LU-6349 mds: remove obsolete MDS_VTX_BYPASS flag

LU-6349 mds: remove obsolete MDS_VTX_BYPASS flag

The MDS_VTX_BYPASS flag is only set and never checked.  This is true
since 2.3.53-66-g54fe979 "LU-2216 mdt: remove obsolete DNE code", but
it was already obsolete for a long time before that.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Ia9510146326e71a134fef85dd8febf7b752cab07
Reviewed-on: https://review.whamcloud.com/31984
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>